Jeff20B

Hey Danomite, any luck locating your missing intermediate plate?

Danomite

nope, Jeff is supposed to be working with someone on replacement cost and whatnot. I emailed him last fri but have not heard back yet.

Jeff20B

I've gotten replies from Jeff ranging from as little as a couple hours to as long as a week or so.

Jeff20B

On to the B material.



Have you seen the pictures of Danomite's shaft? He posted it and some others on nopistons. A picture speaks a thousand words. The pictures will show you the basic layout of everything.



To answer your specific questions, the center intermediate is left alone. There is a gear in the front intermediate and the rear intermediate. The engine takes three front stationary gears and one rear. Two are modified to fit the intermediate plates (one acts like a rear stationary gear). The center of the shaft looks similar to a 2 rotor shaft but instead of being offset 180°, it's offset 90°.



How does this work? How can the engine get away with only two counterweights? Well, first you need to learn how the 20B's rotors are phased and compare that to a 2 rotor. In a 2 rotor, if the heavy part of the front counterweight is pointing up, the front rotor will be mostly in the lower part of the front rotor housing while the rear rotor is mostly in the upper part of the rear rotor housing and the rear counterweight's heavy part is pointing down. If you could follow all that, first realise the 20B only has two counterweights. The front counterweight of the 20B is offset 120° from the front rotor. The middle rotor is also 120° off from the front. The rear rotor is 120° off from the middle and the rear counterweight is 120° off from the rear rotor. If you were to imagine the three tips of a triangle and then imagine the majority of the mass of each rotor falling on one of these three points, together they produce a balancing effect for the middle rotor. The front and rear rotors simply need a counterweight to offset their mass. The weight of a counterweight is approximately half the weight of a rotor. Take a single rotor engine for example. Since there is only one rotor, all of its weight needs to be absorbed by using a standard set of front and rear counterweights - the only difference being the shaft allows the counterweights to both fit 180° off from the rotor, to balance it since there is only one rotor in the system.



Now we get to the 4 rotor. Rotors 1 and 2 are phased 180° apart just like any 2 rotor engine. Likewise rotors 3 and 4 are also phased 180° apart. The 90° offset is in the middle with no counterweight. How does it balance? I'm not sure exactly but I know the 20B balances even though the rotors are offset 120°. I assume the 4 rotor is similar. All I can tell you is it works.



A note about exhaust note. First let me say that your idea to TIG two shafts together most likely won't work. Second, you thought about having them 180° apart which would yeild an engine sounding like two 13Bs reving together. Your idea would produce two exhaust pulses at the same time every 180°. The Jeff Bruce shaft will produce an exhaust pulse every 90° and sound like a true 4 rotor.



I don't think it would be feasible to attempt to set it up on a tigged shaft. I'd recommend a Jeff Bruce shaft and his other parts way before anybody else. I've been aware of his work since Oct 1997. It was such an "ah hah!" moment for me I remember it clearly. It was a 3 rotor 13B shaft made for the NOT20B 1st gen.



Looks like I'll have go back over the ignition stuff. My idea was to use two dual output (leading) coils from an FC and two GM HEI ignitors on a modded dizzy. For a MegaSquirt setup, leave the stock ignitors in the coil holder base as they are and set the MS to 4 cylinder DIS ignition output mode. Feed a crank angle signal into the ECU with the CAS. There are plenty of instructions out there for setting up a CAS with an MS and how to hook it to the ignitor(s). Of course this will cover leading only, but having dual sparks will be ok and cover for the lack of trailing. If going turbo in the future, that's a whole nother animal. I'd recommend trailing at that point, and maybe single leading sparks. The whole setup would require 8 single output coils; 4 for leading and 4 for trailing.



Hold on. If you got creative maybe you could get away with two dual output coils (for leading) and four single output coils (for trailing). There would be no leading/trailing split, but should be ok. Now imagine we have four spark outputs, and one is fed from the ECU at TDC to the front rotor. It is connected to two ignitors. One ignitor is on the dual output coil which feeds rotors 1 and 2. The other ignitor is on the trailing coil. This produces three sparks at the same time; L1, L2 and T1. Now 90° later at "TDC" of rotor 3, another spark trigger is outputted from the ECU, it travels to the ignitors on the dual output coil connected to L3 and L4, and ignitor on the trailing coil connected to T3. Can you see where I'm going with this? No? Well lets continue on to 180° of eccentric shaft rotation where rotor 2 is ready to fire. The ECU outputs another trigger signal. A transistor seperates the signals so we don't get any cross triggering events on the trailing coils. The ignitor on the dual output coil which fires L1 and L2 gets another trigger signal and the trailing coil on T2 also fires. Lastly a fourth trigger signal is outputted from the ECU, which travels to the other dual output coil connected to spark plugs L3 and L4, and also the last trailing coil, connected to T4.



I'm sorry if the above was typed out kind of sloppily. I just now came up with it as a solution for your future turbo upgrade. You could set the MS to whatever mode allows four outputs and triggers each one in succession at 90° intervals (V8?). Then some careful logic circuitry would prevent two trailing coils from sparking at the same time. Infact a diode would probably be more effective than a transistor.



The above would only be six coils and you could probably fit them under the hood more easily than eight. Of course to start with, you really only need two dual output coils. It just depends on how complicated you want to make it for yourself. I can't keep helping you forever.



Oh, I didn't answer this question fully yet. A dual output coil fires both outputs at the same time. That's how it works. It can never be hooked to trailing. It must always be hooked to leading. One output needs to be in the exhaust phase whether piston engine or rotary. If you try to hook it up in some other way, it won't work very well. Others on the forum can explain it better.



The R26B housings with three plugs fired L and T together and I think the 'late trailing' plug, located high on the rotor housing, also fired at the same time. Hey, it's racing. The less complicated, the better. The small hole for trailing and late trailing did allow some compression losses but did improve fuel mileage a small amount. Or was it the same mileage with an improvement in torque? Well anyway, there you have it: three sparks at the same time and no dual leading sparks. They had 12 coils sitting on top of the engine you know. Seriously complicated if you ask me.



Two normal sized turbos would be best. Whatever normal is.



You have an advantage over me. I can only build one exhaust and it has to be good. The cutout, I believe you're refering to, will oncork the exhaust and let the peripheral ports breath. Then for city driving, the electric valve will close and keep things quiet. Either fully closed or fully open.



I'm not sure what to tell you about your exhaust. Just do the research and try various ideas. Start by planning to connect the pipes from each 180° phased rotor pair to each turbo. Then maybe join the two pipes further down. This should give you the awesome 4 rotor sound and it won't require much muffling.



When you start on ignition, you're going to encounter lots of "I don't knows" from the MS crowd. I did. I requested that the three LEDs be converted to ignition outputs. So James wrote the code for it and tweaked the multi tooth wheel code to reduce spikes. I was on my own for the rest of it. Then James added a forth ignition output on one of the other pins of the CPU for his V8. This is what I'm thinking you could use. However I'm unclear as to all the little misc things like will it output a trigger event every 45°, or 90° or maybe even 180°. I had to trick the MS into thinking my engine was a V12 when infact it was supposed to be a V6. This was the only way to get a trigger output every 60° instead of every 120° so each rotor would get a spark at TDC and another 180° later, but phased at 120° intervals. I accomplished this by doubling the incoming trigger signal by taking a 12-1 wheel and cutting out the 6th tooth to create a 6-1 wheel which repeats twice per rev. Setting it to V12 corrected the onscreen tach. Again the output triggers are hardcoded to the input triggers so I had no other choice. Fortunately the injection events are variable to some extent so the engine did run albeit not that well, but I blame my limited understanding of tuning on that. I didn't have an O2 sensor at the time and I even had to disable the BAC valve. At least it could be driven around the block and only stalled between shifts. I hope the engine's age and worn apex seals are to blame for some of it. A rebuild should take care of the hardware side of things. The rest is tuning in software. Ugh.

Danomite

Same here, I have to guess that he is pretty busy, and he will not respond to a question until he knows the answer.

Jeff20B

Ths stationary gears arrived so we'll be able to send everything to Jeff Bruce soon.

Danomite

Heard from Jeff; FedEx is going to pay $1000NZ for the lost iron, not sure how long it will take but at least that's something. In hindsight you might want to check on how much extra it will cost to insure your stuff. I dont think it will cost much more than 100 for insurance.

The Ultimate 7

Sorry for not reading the thread in full. Is your kit for the 13b rotors or 12A? I'm also planning a purchase of this kit later in the future. Would you not mind measuring the distance of the rear tranny bell housing surface to the front of the e-shaft? I need this measurement for my research and records for future fitment possibilities. Thx!

vortexau

My dream thread! So much information in this thread, its got me so pumped to do a 4 rotor...



I dont have pics, but I have a 'shrine' at home to the Le Mans winning Mazda 787B - static models of the winning car and a massive poster of (in my opinion) the greatest rotary powered car on earth

Hybrid G

any update thus far on this build?



Pretty cool thread



Hybrid